You might have to sit all day for your job, but try to walk as much as possible the rest of the time to offset the higher risk of death and heart disease that comes with being sedentary. — Filepic
Every additional step, up to around 10,000 steps per day, reduces the risk of death and cardiovascular (heart) disease (CVD), regardless of how much remaining time is spent sedentary, reports a large population-based study published online in the British Journal of Sports Medicine.
Some previous studies have shown that greater daily step counts are associated with lower levels of death and CVD, while others have linked high levels of sedentary behaviour with increased risks of CVD and death.
However, none of these studies investigated whether high levels of physical activity may offset or lessen the higher risk of death and CVD associated with time spent sedentary.
To address this, the authors of this new study, led by the University of Sydney’s Charles Perkins Centre in Australia, accessed data on 72,174 individuals (average age 61; 58% female) enrolled in the UK Biobank study – a major biomedical database – who had worn an accelerometer device on their wrist for seven days to measure their physical activity.
The accelerometer data were used to estimate daily step count and time spent sedentary, i.e. sitting or lying down while awake.
The median daily step count for participants was 6,222 steps per day.
The reference point for assessing the impact on death and CVD events of increasing step count was taken as 2,200 steps per day – the lowest 5% of daily steps among all participants.
The median time spent sedentary was 10.6 hours per day, so study participants sedentary for 10.5 hours per day or more were considered to have high sedentary time, while those who spent less than 10.5 hours per day sedentary had low sedentary time.
Lowering risk
Over an average of 6.9 years of follow-up, 1,633 deaths and 6,190 CVD events occurred.
After taking into account other potentially influential factors, the authors calculated that the optimal number of steps per day to counteract high sedentary time was between 9,000 to 10,000 steps per day.
This lowered death risk by 39% and CVD event risk by 21%.
In both cases, half the benefit was achieved between 4,000 and 4,500 steps per day.
This is an observational study, thus it can’t establish cause and effect.
And although the large sample size and long follow-up allowed the risk of bias to be reduced, the authors acknowledge the possibility that other unmeasured factors may have affected their results.
As steps and sedentary time were obtained in a single time point, this could also lead to bias, they add.
Nevertheless, they conclude: “Any amount of daily steps above the referent 2,200 steps per day was associated with lower mortality (death) and incident CVD risk, for low and high sedentary time.
“Accruing between 9,000 and 10,000 steps per day optimally lowered the risk of mortality and incident CVD among highly sedentary participants.
“The minimal threshold associated with substantially lower mortality and CVD risk was between 4,000 and 4,500 steps per day.”
They add: “Our prospective results provide relevant findings that can be used to augment public health messaging and inform the first generation of device-based physical activity and sedentary behaviour guidelines, which will likely include specific recommendations on daily stepping.”
